Centrifugation is used to separate the components of liquid suspensions and mixtures according to their density, using centrifugal force. A centrifuge consists of a rotor, with a sample holder adapted to hold a plurality of sample containers. The sample holder is in the form of a plurality of tubes or buckets which are adapted to receive the sample containers which are in the form of vials or buckets. The tubes or buckets, referred to hereinafter as individual holders, are located around the circumference of the sample holder. The rotor is attached to a motor. In use, the sample containers are loaded into the sample holder, and the rotor is rotated at high speed to exert a centrifugal force that moves the heavier components of the sample to the outside of the rotor. Depending on the application, the sample holder can be at a fixed angle or can be of a “swing-out” type in which the sample holder will swing out to an angled or horizontal position relative to the axis of the rotor shaft when rotation begins. Centrifugation is used in both experimental and industrial processes in a wide range of fields. One very common use is in the field of biology in which it is often necessary to separate biological cells from their liquid media. This step is an integral part of almost every experimental and manufacturing procedure involving cells.
It is becoming more common to alternate procedures relating to the separation of biological cells from their liquid media, and therefore it is often advantageous to be able to use a centrifugal device on a robotic platform for use in a system incorporating a pipetting robot. A pipetting robot is used to automatically extract a fluid from a vessel and to transfer that fluid into a container held in an individual holder forming part of a centrifugal device in order that the components of the fluid can be separated using centrifugal force.
A problem with existing centrifugal devices is that after rotation, the one or more individual holders are randomly positioned relative to their pre-rotation positions. This makes it impossible for such centrifugal devices to be used in conjunction with a pipetting robot, since the robot cannot identify the location of individual samples after rotation.